Unregardless of how accurately i check my csv file, the import form keeps on telling me that something is wrong in the VAT numbers i am importing. So i spent a whole hour in checking them on the VIES site on the advice of one of the open ERP assistants. This site only verifies VAT numbers of subjects that are registered in the INTRA office. By checking the numbers on the Italian Ministry of Economics, all my VAT numbers come out to be properly recorded.
Eventually i had to exclude the VAT number column from importing, and inserted them by copy/paste. Funny that the "validate VAT number" button on the client form now tells that the number is correct.
So i guess that there is somenthing wrong in the constraints that open ERP uses to validate the table upon the import process.
I point that i have no base_vat module installed
Would it be possible to remove the control, or at least know what the constraints are in order to make all the number compliant?

I am not really able to go trough the codes that Ray sent me, nevertheless i can see that, at some point, the sistem checks on the VIES site if the VAt number is valid. As i i have said in my previous message, this site only lists IT VAT codes as correct if they are in the INTRA register fo intra-european union operations. So many of them will probably result incorrect. Would be better to check them on the italian ministry of economics (i am sorry, i am not allowed to post links) but if you put "verifica partita iva agenzia delle entrate" in google, it should be the first link.
Thanks anyway, and sorry for my partial understanding of codes.

Alberto, from Vies web page / FAQ: "The data is real-time. Each time you make a request, a message is sent to the Member State which issued the VAT identification number asking if the number quoted is valid."

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